The actress apparently painted this with her own hand. This photo originally turned up on Tumblr and Reddit user immigat discovered proof of the self-portrait's existence in a 2011 Vogue article:

As Emma takes me on a tour of her house, the extraordinary depth and breadth to her talents become obvious. Every room is framed around a beautiful artifact—a piece of furniture or fabric picked up at a flea market in Paris or Los Angeles—and her artworks show that she can both paint and draw exquisitely. One picture stands out: It is a self-portrait of Emma holding a camera. The lens is aimed menacingly at the viewer, like the barrel of a gun, a neat illustration of what we had just experienced at the Tate.

Given the angsty shades of Max Beckmann and the bright, Fauvist colors, maybe she was availing herself of RISD classes while attending Brown. Perhaps the narrowed, pained eyes communicate a personal message? Hermione, we're depressed that you didn't end up with Harry, too. You don't need to hide it in your art.